It is known that adenosine shows attenuation of the activity of neurotransmitters via an A.sub.2A receptor [European Journal of Pharmacology, 168: 285 (1989)]. Consequently, adenosine A.sub.2A receptor antagonists are expected as remedies or preventives for various diseases induced by hyperactivity of adenosine A.sub.2A receptors, such as a remedy for Parkinson's disease, an anti-dementia drug, a remedy for depression, and the like. Furthermore, the above antagonists are expected to show therapeutic and symptom-improving effects upon Alzheimer's disease, progressive supranuclear palsy, AIDS encephalopathy, propagative cavernous encephalopathy, multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, multiple system atrophy, cerebral ischemia, somnipathy, ischemic heart disease, intermittent claudication, or the like.
On the other hand, [1,2,4]triazolo[1,5-c]-pyrimidine derivatives are disclosed as compounds having diuresis activity in Japanese Published Unexamined Patent Application No. 13792/85, as compounds having antiasthma activity in Japanese Published Unexamined Patent Application No. 56983/85, and as compounds having bronchodilation activity in Japanese Published Unexamined Patent Application No. 167592/84.
However, adenosine receptor antagonism of [1,2,4]triazolo[1,5-c]pyrimidine derivatives and their activity on the central nervous system are not known.